The present invention relates to optical fiber couplers in general, and more particularly to an arrangement for and a method of packaging such optical fiber couplers.
Optical fiber couplers of various constructions are already known and in widespread use, especially in the telecommunications field. Generally speaking, such optical fiber couplers render it possible to interconnect individual optical fibers in such a manner that the modulated light propagating through an input optical fiber leading to the optical fiber coupler continues to propagate through at least one output optical fiber leading from the optical fiber coupler after passing through the latter. In some of the conventional optical fiber coupler constructions, at least two input optical fibers merge or are fused with one another at a coupling region of the optical fiber coupler so that the output light signal or each of such output light signals is a combination or function of the input light signals. The present invention is primarily, but not exclusively, concerned with optical fiber couplers of the latter type, that is, with optical fiber couplers in which mixing of the input light signals takes place.
Optical fiber couplers of the above-discussed type are very sensitive to environmental influences not only because they are made of an optical material, usually glass, which is very fragile, but also because the coupling region proper and its vicinity are usually bare, that is, not provided with a jacket, so that environmental influences could affect the quality of the optical material of the optical fiber coupler and/or of the signals transmitted through the coupler, lest the exposed or bare region of the optical fiber coupler is protected from environmental influences.
In view of the above, it has been already proposed to encase the optical fiber coupler in such a manner as to protect the exposed region from deleterious environmental influences. However, experience with conventional constructions of such coupler-protecting arrangements has shown that they leave much to be desired as far as the protecting function thereof is concerned, especially in military use where the optical fiber coupler and the protective arrangement therefor are often subjected to extremely high or extremely low temperatures and/or very high temperature variations in relatively short periods of time, and/or to vibrations or impacts of considerable magnitudes. Thus, it has been observed that the failure or breakage rate of optical fiber couplers encased in the conventional ways is very high, which presents a severe limitation to the use of conventionally encased optical fiber couplers especially in military communication applications.